1.在mainwindow.h 添加声明
            
            
              cpp
              
              
            
          
          class QLineEdit;
class QDialog;
    void textFind();    //查找文本
    void textNext();    //查找下一个
        2.在cpp里面进行添加、布局、定义
添加查找和布局窗口
            
            
              cpp
              
              
            
          
           //查找
    QAction *action_textfind = new QAction("查找",this);
    connect(action_textfind,&QAction::triggered,
            this,&MainWindow::textFind);
    ui->mainToolBar->addAction(action_textfind);
    m_findDialg = new QDialog(this); //查找对话框
    m_lineEdit = new QLineEdit(m_findDialg); //查找输入框
    QPushButton *btn = new QPushButton(m_findDialg);
    btn->setText("查找下一个");
    connect(btn,&QPushButton::clicked,
            this,&MainWindow::textNext);
    //进行垂直布局
    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(m_lineEdit);
    layout->addWidget(btn);
    m_findDialg->setLayout(layout);
        对第一步的声明进行定义
            
            
              cpp
              
              
            
          
          void MainWindow::textFind()
{
    m_findDialg->show();
}
void MainWindow::textNext()
{
    QString strFind = m_lineEdit->text();
    bool isFind = ui->textEdit->find(strFind,QTextDocument::FindBackward);
    if(isFind){
        qDebug()<<QString("行号:%1,列号:%2")
                  .arg(ui->textEdit->textCursor().blockNumber())
                  .arg(ui->textEdit->textCursor().columnNumber());
    }
}